Stoker air control



F. R. Newsom 2,233

Filed Jan. 5o, 1939 2 sheets-sheet l Feb. l l, li.

F. R.` NELsoN 2 sheets-sheet 2 STOKER AIR CONTROL Filed Jan. 50,1939

Feb; 1 1, 1941.'

atentos! Feb. 1l, 1941 NITED STATES STOKEB 'Am CONTROL Floyd R. Nelson, Rockford, Ill., assigner to Cotta mission Corporation, Rockford, Ill., a

corporation of'lllinois Application January 30, 1939, Serial No. 253,631

8 Claims.

This application is a continuation in part of my application Serial No.- 69,944, iiled March 20.

This invention relates to stokers and has particular reference to a novel means for controlling the volume of air delivered to the retort of an underfeed stoker.

The principal object of my invention is to provide a damper in the air conduit, the position of which changes due to variation of back pressure in the conduit whereby t automatically open the damper wider when resistance to the passage of air through the fuel bed increases, and vice versa. Another object is to provide an oscillating vane linked to the damper and mounted so as to tend to gravitate to a position corresponding to the fully closed position of the damper and arranged to be raised more and more with increase in back pressure in the conduit to ac` cordingly open the damper wider and wider, whereby to maintain a substantially constant flow of air through the fuel bed regardless of varying bed conditions, arising either from variation in the coal fed to the retortA or variation in the amount of clinker allowed to accumulate.

l Still another object consists in the provision of an air chamber for the vane, having an ad- I justable air bleeder valve arranged to be adjusted manually to suit the requirements of a given installation, according to the kind of coal to be burned and the depth of ilre bed to be maintained, this valve determining by its adjustr ment the normal degree of rise of the vane and far as the amount of damper opening is ccnvcerned. A special feature in this connection is the mounting of the oscillating vane in eccentric relation to the arcuate wall of the air chamber so as to have increased clearance for air flow past the vane the farther it moves upwardly and opens the damper more and more, whereby to secure the desired responsiveness and sensitivity and insure against movement of the damper past the point to which it should be adjusted to suit a. given condition of the fire bed.

The invention is illustrated in the accompanying'drawings, in Which-- y 50 Figure 1 is a side view of a stoker installation in which the air conduit of the stoker `embodies an air control made in accordance with my invention; i

Fig. 2 is an enlargement of the air control 55 portion of Figure 1;

accordingly the normal or mean condition so.

(Cl. 23S- 45) Fig. 3 is a longitudinal section through the structure of Fig. 2;-

Fig. 4 is a cross-section on the line 4-4 of Fig. 3;

Fig. 5 is a side view of another air control 5 generally similar to that shown in Fig. 2;

Fig. 6 is a longitudinal section through the structure of Fig. 5;

Fig. 7 is a cross-section on the line I-'I of Fig. 6, and. `10

Fig. 8 is a sectional detail on the line 8-8 of Fig. 7.

Similar reference numerals are applied to corresponding parts throughout the views.

The stoker appearing in Figure 1 has the con- 15 ventional `hopper 5 to store the coal which is fed through a conduit 8 into the bottom of the retortfl. The coal fed to the retort rises therein to maintain a desired depth of fire bed, the coal being fed from the hopper through the conduit 20 by a screw in the usual way. The screw is driven through reduction gearing in the housing 8 by an electric motor indicated 'in dotted lines at 9, the same being disposed behind the blower housing I0. Simultaneously with the feeding 25 of coal to the retort, air is discharged tangentially from housing I0 through the downwardly inclined neck II into the air conduit I2 and conducted into the retort 1, whereby tosupply sufficient air to the re bed for good com- 30 bustion. In the past, various typ of air controls have been provided, some involving merely a manually adjustable damper or shutter and others involving dampem or shutters intended to be adjusted automatically to suit conditions. Most of the automatic controls with which I am familiar have been rather complicated and expensive, and, on the whole, not very reliable. Then too, most of them if adapted to meet one conditionjwould not take care of others apt to arise in service, with the result that they have not given satisfaction. The air control of vmy invention is one Vwhich is simple and inexpensive, and, when once manually adjusted to suit the requirements of a given installation, automatically adjusts itself thereafter to varying bed conditions, to the end that the stoker is kept operating eficiently at all times.

According to my invention, a damper I3 is mounted on a horizontal shaft I4 in the neck II 50 for oscillatory movement. The screws I5-I6 have conical seats receiving the conical ends of the shaft I4 with a free Working iit to insure smooth and easy turning of the damper. A pointer I1 is xed to the shaft I4 outside the 65 o the damper. This pointer points to 9" whe the domper is closw. iand to 5" when the per is fully opened. An arm is on the damper is has a link tu attached thereto connecting the demper with the actuating vane si. The vene is designed to work by air pressure, as s piston or diaphragm, except that its movement is oscillatory. It is mounted on a horizontal shaft 22 received with e free working fit in bearings 23 in the opposite sides or" a segmental houding 2e csrried on top of the neck il adjacent the bend therein. The vane 2i hss o certain amotuit of clearance between the edges thereofy and the side and end walls of the housing, es clearly oppears in Figs. 3 and e, so that while this vene will he deected upwardly under air premure from beheath, air will pass around the edges of the vane and escape from the housing through the slot 25 more or less freely depending upon the odjustmenti of a bleeder valve 2t. The latter may be of any suitable or preferred type and, in this case, is in the form of a round rod received with a close working t in the elongated bearing 2i provided on the top wall of the housing. One side oi? the rod has a hat milled thereon, es indicated at 23, so that as the rod is turned, more or less of the slot 25 is opened to the atmosphere through another elongated slot 2@ in the well of 'the bearing 2l. The rod 2o has e. pointer t@ on the enlargedend thereof,- which moves relative to graduations 3i on the side wall of the housing 2t to indicate the position of the vulve. The

'housing 2t will preferably be csst in one piece,

as e. die casting, for economy and to insure the desired accuracyof nt of the vane 2i therein. This housing is shown as fastenedby means of screws 32 to the wall of the neck ii over the openingk 33 therein, und a gasket 3s interposed between the parts metres for an slr-tight connection. The vane 2i, owing to the position oi the housing tends to grsvitete to the lowermost position in which itis shown in Fig. 3, and, while it takes very little air pressure upon the vene to cause it to start rising, it is manifest that more and more pressure is required to raise the vane the nearer it approaches a horizontal position. Now, the vane will reach substantially a horizontal position when the damper i3 is substatiaily fully opened and pointer il points to 5. i may' provide en arm 3 on one end of. the shaft 22 adiustelbly secured by means of e. set screw 36, to permit placing it at any desired angle relative to the vane, and having a plurality of spaced holes il into any one oi7 which a screw su; may be entered to fasten s counterweight or Weights 39 closer to or farther from the axis of oscillation oi said vane. In this wey, any defsired operating characteristics so far as the operation of the'vane 2i -is concerned may be obtained, and more or less air pressure will be required to bring the vane to a certain position.

In operation, whenever the usual room thermostat stops the stoker because the heat demand has been satised, the vane 2i gravitates to the position shown in Fig. 3 and closes the damper i3, thus leaving the fire bed dependent upon the small 'amount of air that will seep past the damper i3, and what air will find its way through openings in and around the re door of the furnace. The fact that the damper is closed makes for economy because the coal will naturally burn slower under those conditions, and it also makes for mtter comfort by avoiding overheating.

assises partial opening, where it is in equilibrium, with' the pointer il at one of the numbered positions between and 5, or at some position between two numbers. The setting of the valve 2B is made to suit the requirements of the installation, according to the hind of coal to be burned and the depth of fire bed to be maintained. The thing that determines the position of the damper It is the back pressure in conduit I2, which acts on the vane 2i, and, obviously, if the air valve 28 is adjusted so that sir passing around the edg of this vane is allowed to escape freely, so that a greater pressure differential exists between the opposite sides of the vane, the vane will rise higher and accordingly open the dampery I3 wider. been set so that under normal conditions the demper is will open to an extent where the pointer ii is opposite say the numeral 2,nnd, due to, let us say, an inux of finer coal than usual, the resistance to air flow through the ire bed is increased: this will result in raising the vane 2i a trifle higher and accordingly the damper i3 will be opened wider to admit more sir to meet the demand. In other words, the control meters the volume of air required for a certain fuel bed. In that w`ay, good combustion is secured. By the same token, if more than the usual amount of clinker is left on the `ilxe bed and the resistance to 'air ow through the re bed is accordingly increased, the damper I3 will be opened wider automatically to take care of the need for increased volume of air. This air control,l in other words, compensates automatically for varying fuel bed conditions and thereby insures keeping the Stoker operating eillciently et sli times. It is manifest that the air control involves so few parts and these are of such simple and durable construction that there is very little likelihood of the mechanism getting out of order and requiring attention. A few simple instructions will enable the user to make whatever adjustments may be desirable. Usually, the valve 2S when once properly set according yto instructions will not require any readjustment unless the user changes to some other kind of coal or decides upon maintaining a different depth of rire bed. f

y While I have disclosed a damper I3 in the air conduit operated by the vane 2l to meter the volume of air delivered to the retort 1, it should be evident that the same results could be obtained by leaving the vane 2| where it is and substituting for the damper a shutter on the air intake t0 on the blower housing I0 to meter the intake of air to the blower. Obviously, the volume of air delivered to the retort would be varied in the same Way by such a shutter operated in response to movement of the vane 2l. The claims should be construed accordingly, the word damper" used therein being considered in its broad sense as referring to any air control or metering member, such as a shutter.

Referring now to Figs. to 8, in which the numerel I la designates the end of the air discharge neckvon the blower housing and |2a designates the. adjacent end portion of the air conduit through which air is delivered to the re bed, this air control, like the other, involves an oscil- Now, assuming that the valve 28 has p 23315635 lating vane `21a operatively connected with a i damper itay through the medium oi a linkv 20a. Thevane. 2la, like the ,vane 2|, is arranged to be operated by air pressure to communicate movement to the damper, the segmental housing 24a in which the vane operatesbeing in communication. with the air .conduit through the opening 33uv so as to subject vthe Avaneto whatever static pressure existsin theair conduit. Asln the Vair control first described,`a slot 25a permits escape of aix-from that space in the housing behind the vane, and air will pass around the edges of the vane and out through the slot more or less freely depending upon the adjustmentor the bleeder valve 26a, which, in the presentflnstance, is inE the form'oi a dat strip otfsheet metal pivoted on a screw 40 at .one end -for oscillatory adjustment relative to-.the slot 25a and arranged to be held in adjusted positionby means of a set screw 4I threaded in the cover plate 42 mounted on the housing 24a and arranged to be locked by'means of a lock nut 43. The end of the valve 26a pro jects through a. slot 44v in one Aend of the cover plate `42 to permit manual adjustment thereof when the set screw 4l is loosened and obviously the position of the valve in relation to the slot is a suillcient indication ofthe adjustment, because .when the valve is in a mid-position in the. slot.

as shown in Fig. 8, the slot 25a is half covered. The vane Zia in the present structure is counterbalanced by a weight 45 iixed by means of a set screw 46 in the proper position of endwise adjustment relative to an L-shaped arm 41 carried on A'the pointer lla fixed to the shaft, l4 carrying the damper I3a. The portion of the arm 41 carrying the weight 46 lsparallel' to the pointer l'la, and hence when the weight ls adjusted along the arm, itslradius .with relation to the shaft I4 is changed and its counterbalancing valuel is increased or decreased. In the clockwise `movement of the vane 2Ia the counterweight V45 is moved ln a 'counterclockwise direction through` a. correspondingV angularity and Vtherefore exerts a greater and greater c ounterbalancing effect theffarther the vane is raised. Now, it is important to .note that the center 22a about which the vane 2la oscillates is slightly eccentric relative to the `arcuate 'inside wall 48 of the housing 24a. This is indicated in Fig. 6 by the fact that'the dot-and-dash arc af--b de scribed by the outer end of the vane in its move- Y ment is in closer spaced relation to the arc 48 at va than at b. In actual practice, the housing 24a is preferably die cast with the bearing holes 49 for the shaft 22a eccentric just a few thousandths of an inch, so that the clearance between the outer end 50'ofthe vane 2 la and the arcuate wall K 48, at b, is just a few thousandths oi vaninch (ill greater than at a. This varying clearance has proved to be very important in` securing the desired responsiveness and sensitiveness and forinsuring -accurate movement of the damper and preventing movement past a certain point to which the damper should be adjusted to suit a given condition of the bed.I I have found that this varying clearance is directly responsible for l'the stopping of. the vane VZla at a; certain position when there is a change in the fire bed, due to a sudden influx of fines, for example, or, due to an accumulation of ashes or clinkers, and

y a wider openingv of the damper is required and is produced automatically. I have found that if a greater variation in clearance is provided between points a and b, a different sized counterweight is requiredl or a different position of adis clear, therefore, that what happens when the fire vbed develops resistance to air flow through it and requires a wider opening of thedamper is this: The' increase in back pressure in the air conduit I2a acting on the vane 2Ia, which up to that time was in a balanced positionoi' equilibrium, causes the vane to move in a clockwise direction, opening thedamper wider, the vane moving upwardly to a pointwhere, -due to the greaternclearance between the vane and the wallj48,- there is a sufficiently increased ilow of air possible past the vane-'and out through the slot 25a to establish a new position of equilibrium with the counterweight 45 also exerting a greater counterbalancing eilect by reason of its shift in position with the damper. Actual experience shows that when the vane has moved to a certain point and adjusted the damper accordingly, it will lnot b e balanced in any other position one way or the, other from that position. For example, if one moves the pointer Ila one way or the other from the self-assumed position, it will invariably come backto exactly that position, thus showing clearly that the parts are imbalanced in any other position" and therefore return to the previous self-assumed balanced position.

Itis believed the foregoing description conveys aI good understanding of the objects and advantages of my invention. The appended ing and operatively connected with saidY damper so as to close the damper when the vane is in lowermost position,said vane being operable with a predetermined clearance in said housing to permit air flow from the conduit into the housing and past said vane, whereby said vane is adapted to be raised by increased pressure in said conduit togopen said damper and lowered upon a decrease in pressure to close said damper, the vane and housing being formed and disposed relative to one another so as to increase the sizeof the air passage between the vane and housing as the vane moves n'a direction to open t'he damper, and adjustable means for permitting discharge of air to the atmosphere from said housing from behind the vane therein. 4

2; A stoker air control comprising a damper mounted With-in an air conduit for delivering air under pressure to a. Stoker retort, said damper having oscillatory movement from a position closing the opening therethrough to another position substantially opening said conduit, a segmentalshaped housing communicating with said conlowermost position, said vane being operable with a predetermined clearance in said .housing to permit air flow from the conduit into the housing and past said vane, whereby said vane is adapted to be raised by increased pressure .in said conduit to open said damper and lowered upon a decrease in pressure to close said damper. the 5 vane and housing being formed and disposed relative to one another so as to increase the size of the air passage between the vane and housing as the vane moves in a direction to open the damper, a counterweight carried on anarm arranged to osoillate with one of the aforesaid oscillatory damper and vane, and adjustable means for permounted for oscillatory movement in said hous-l ing on an axis eccentric with respect tothe arcuate wall of said housing and operatively connected with said damper so as to close the damper when the vane is in lowermost position, said vane being operable with a. predetermined clearance in said housing variable due to the eccentric mount ing of the vane to permit air ow from the conduit into the housing and past said vane. whereby said vane is adapted to be raised by increased pressure in said conduit to open said damper and lowered upon a decrease in pressure to close said damper, the clearance between the vane and housing increasing as Ithe vane moves in a. direction to open the damper, a counterweight on an arm oscillating with one of the aforesaid damper and vane so as to give increased counterbalancing effect with increased opening of the damper, and adjustable means for permitting discharge of air to the atmosphere from said housing from behind the vane therein.

4. A Stoker air control comprising a damper mounted within an air conduit for delivering air under pressure to a stoker retort, said damper having oscillatory movement from a position closing t-he opening therethrough to another position substantially opening said conduit, a segmental-shaped housing communicating with'said con- 5o duit adjacent the damper, a gravitating vane mounted for oscillatory movement in said housing on an axis eccentric with respect to the arcuate wall of said housing and operatively connected with said damper so as to close the damper 55 when the vane is in lowermost position, said vane being operable with a predetermined clearance in said housing variable due'to the eccentric mounting of the vane to permit air flow from the conduit into the housing and past said vane, where- 0 by said vane is adapted to be raised by increased pressure in said conduit to open said damper and lowered upon a decrease in pressure to close said damper, the clearance between the vane and housing increasing as the vane moves in a direc- 65 tion to open the damper, and adjustable means for permitting discharge of air'to the atmosphere from said housing from behind the vane therein.

5. A draft regulator comprising a damper mounted wit-hin a conduit for oscillatory moveo ment' from a position closing the opening therethrough to another position substantially opening said conduit, a segmental-'shaped housing communicating with said conduit adjacent the damper, a vane mounted for oscillatory movement in said housing and operatively connected with said damper, said vane being movable with a predetermined clearance in said housing so as to permit air flow through the housing past said vane, the vane and housing' being formed and disposed relative to one another so as to increase the size of the air passage between the'vane and housing as the Vane moves in a direction to open the damper, and adjustable means on the housing for regulating the flow oi air past the vane.

6. A draft regulator comprising a damper mounted within a conduit for oscillatory movement from a. position closing the opening therethrough to another position substantially Opening said conduit, al segmental-shaped housing communicating with said conduit adjacent the damper, a vane mounted for oscillatory movement in said housing and operatively connected with said damper, said vane being movable with a predetermined clearance in said housing so as to permit air flow through the housing past said vane, the vane and housing being formed and disposed relative to one another so as to increase the size of the air passage between the vane and housing as the vane moves in a direction to open the damper, a counterweight carried on an arm arranged to osciilate with one of the aforesaid oscillatory damper and vane, and adjustable means on the housing for regulating the flow. of air past the vane.

7. A draftregulator comprising a damper y mounted within a conduit for oscillatory movement from a position closing the opening therethrough to another position substantially opening said conduit, a segmental-shaped housing communicating with said conduit adjacent the damper, a vane mounted for oscillatory movement in said housing on an axis eccentric with respect to the arcuate wall thereof and operatively oonnected with said damper, said vane being movable with a predetermined clearance inl said housing so as to permit air now throughthe housing past said vane, the clearance betweenthe vane and housing increasing as the vane moves in a direction to open the damper, and adjustable means on the housing for regulating the ow of air past the vane.

8. A draft regulator comprising a damper mounted within a. conduit for oscillatory movemen-t from a position closing the opening'therethrough to another position substantially opening said conduit. a segmental-shaped' housing communicating with said conduit adjacent the damper, a vane mounted for oscillatory movement in said housing on an axis eccentric with respect to the arcuate wa'll thereof and operatively connected with said damper, said vane being movable with a predetermined clearance in said housing so as to permit air flow through the housing past said vane, the clearance between the vane and housing increasing as the vane moves in 'a direction to open the damper, a counter- Weight on an arm oscillating with one of the aforesaid damper and vane so as to give increased counterbalancing effect with increased opening of the damper, and adjustable means on the housing for regulating the ow of air past the vane.

FLOYD R. NELSON. 

